1. Field of the Invention
The present invention relates to the control of a turboshaft aero-engine, and more particularly to a compensating device for the temperature in front of the high pressure turbine of a compound turboshaft engine which comprises high and low pressure units and includes a control system for regulating the engine to a desired constant temperature behind the low pressure turbine, the device being intended to increase automatically and temporarily the thrust of the engine in poor flight conditions, especially at high ambient temperatures and when the engine is cold.
2. Summary of the Prior Art
In a turboshaft engine regulated to a constant after turbine temperature, thrust is normally at a maximum when the pilot sets the engine control system to full throttle. However, a lack of thrust is observed when the engine is cold and/or when the ambient temperature is high. This occurs in Particular on take-off and during landing approach stages, i.e. at the time when the pilot needs maximum thrust. This lack of thrust is due to the fact that the temperature is insufficient in front of the turbine when applying the engine power, and this temperature deficiency in front of the turbine is all the greater when the ambient temperature is high or the engine is cold.
A gas turbine control device is known which enables the desired temperature value to be rectified when ambient temperature is high. FR-A-2 173 143 describes such a control installation which comprises a function generator, shown in detail in FIG. 3 of the said document, providing a correction rule which is a function of the ratio of the rotational speed of the gas turbine to the square root of the ambient temperature. The drawback with this system is that it does not take into account the thermal condition of the engine as the power applied is increased, which is particularly important for an aircraft at the take-off stage when the engine is still cold.